Dagnabbit, dagonnit, dadgummit, dad-blasted, dadburnit
That's a mouthful, but we lumped these all together because they are all substitutes for (God) damn it. Unfortunately, Dad gets a bit of a bad rap here, but better him then God. Taking the Lord’s name in vain could result in tanning one’s hide or washing one’s mouth out with soap (or castor oil in the old days).
The nabbit, gonnit, gummit, blasted, and burnit match the rhythm of damn it, but they can easily be modified for use as an adjective or adverb: “That dagnab idiot didn’t look to the dadgum left and, dadburnit, he crossed over in my dad-blasted lane and dadburn near killt me.” When used as a stand-alone oath, hold out on the first syllable and accentuate the second: “DaaadGUMMit! Where’s my blasted phone?” That's real southern twang.